Re: [PATCH] Enable AT_PLATFORM for Loongson 2F CPU

[David Daney <ddaney@caviumnetworks.com>]

On 11/07/2010 04:30 AM, Robert Millan wrote:
> El 04/11/10 19:43:08, en/na Robert Millan va escriure:
>> David Daney a écrit :
>>> You are claiming that all loongson2 are loongson-2f.  Is that
>>> really true?  Or are there other types of loongson2 that are not
>>> loongson-2f?
>>
>> I'll figure out how to distinguish them and send a new patch.
>
> I looked at details about CPU identification, and this
> seems to be broken.
>
> See the the notes about PRId in pages 72 and 66, respectively:
> http://dev.lemote.com/files/resource/documents/Loongson/ls2f/Loongson2FUserGuide.pdf
>
> In both 2E and 2F, the implementation field is the same (0x63).
>
> Revision field is the same too, according to docs, and it can't
> be used anyway (no garantee of consistency).

I seems weird to me that you cannot get this information from the PRId 
register.  Perhaps the documentation is defective.

The Chinese version of the Loongson2E user guide seems to say something 
about the two lower nibbles of the PRId, but being a non-chinese reader, 
I have no idea if it would be relevant.

I would think that the low order bits of the register can reliably 
differentiate these two parts.

David Daney



>
> I'm sending a new patch that uses machtype instead. Yes, I know
> it's a bit of a kludge, but it really seems to be the only way.
>
>> Well I appreciate consistency with GCC flag names,
>
> Actually, I missread GCC flag (it's dashless).  I'm using
> "loongson2f" as David requested.
>